This invention relates generally to the generation of power, and more particularly to a power generation unit specifically well suited for generating power from low temperature energy sources especially geothermal energy.
The rapidly diminishing sources of fossil fuels, combined with the polluting effects of both fossil fuels and nuclear fuels, has resulted in considerable attention being directed toward utilizing energy such as low temperature energy, which heretofore has not generally been used, to generate power, specifically electric power. Low temperature energy may be available, for example, in the form of waste heat produced by many manufacturing processes or as solar or geothermal heated hot water or steam. The present invention is directed to a unique power generation unit well suited for use with low temperture energy, particularly geothermal energy. Often, geothermal energy is in the form of a hot brine solution located below the earth's surface. A well is drilled through the surface of the earth to the brine solution, and the hot brine passes upwards, through the well to the surface. Typically, the brine partially vaporizes as it flows upwards, and the well yields a mixture of steam and hot brine. The energy within the mixture is then transformed into a more practical form, such as electric power.
However, available systems for transforming the geothermal energy contained within the mixture of steam and hot brine generally operate at relatively low efficiencies and often have additional serious disadvantages. For example, in one method, the hot geothermal brine is passed through a heat exchanger, transferring heat to a working fluid, and the working fluid is used to drive a conventional turbine generator unit. This method, though, has the disadvantage that a relatively large and expensive heat exchanger is required to effect the necessary heat exchange between the hot brine and the working fluid. A second method of recovering energy contained in the hot brine and steam mixture is to decrease the pressure of the mixture, which increases the amount of vapor in the mixture. The vapor is then separated from the liquid brine and fed to a turbine for the production of mechanical energy. With this method, however, the vapor is at a comparatively low pressure. Since conventional turbines operate relatively inefficiently at low pressures, this method typically results in an inefficient recovery of the geothermal energy.